Re: [Raspberry_Pi_4-Ham_RADIO] Re: Powering the Raspberry & TNC.

Hi Ray, I think I have the same type and managed about 2A (ish) output at 5V with very respectable ripple (read: hardly noticeable on the cro). I was a little

Message 1 of 53
, Apr 5, 2013

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Hi Ray,
I think I have the same type and managed about 2A (ish) output at 5V
with very respectable ripple (read: hardly noticeable on the cro). I was
a little disappointed seeing the output at 4.85V but was withing spec.
I have been bitten a few times because I didn't read the data sheet
correctly, so I read the thing many many times whilst waiting for mine
to arrive.
The one thing (ok, there was two) that stuck in my mind was the use of
low leakage electros and the low loss "tracks" required )shown in bold
in the recommended circuit).
I built mine on vero board and the the low loss connections were
constructed using additional tinned copper wire following the copper and
a heap of solder to fill the gaps. If nothing else, it won't blow away
in the wind ;-)
My coil came out of a few trashed UPS'. I was ratting them for the
toroids but luckily I kept a few intact.

Ian

On 05/04/13 08:51, Ray Wells wrote:
>
>
> I bought 5, smps adjustable output modules using the LM2596 from Ebay
> ($1.52 each including freight from Hong Kong to Australia!). These are
> branded Leivin and the PCB layout and circuit is as per the National
> Semi datasheet. A preliminary test with a 1A load showed a very noisy
> output on the CRO. When time permits I'll try the NS recommendation of
> an LC filter in the output. I think the device has potential but not
> "off the shelf" for running the RPi.
>
> Ray vk2tv
>
> On 05/04/13 00:58, Roger Elmore wrote:
>>
>> Charles wrote:
>> > I am looking at another device to replace the converter because
>> > this device is not adjustable and is set for 5 V. I need to
>> > increase that to 5.25 to compensate for the drop across the
>> > polyfuse.
>>
>> I've begun collecting the parts for a pair of PI+TNC-PI combos (for an
>> APRX digi/IGate and a Linux RMS Gateway) in a rack mount case powered
>> from the same Astron RS-50M as the two radios and going to give the $7
>> LM2596 module (bought from Amazon) a try. 3-40V in and 1.5-35V out at
>> 3A. My plan is to use a separate LM2596 fused at 1A for each PI's
>> input, with a 6A rear panel accessible fuse common to the 13.8V input
>> of each LM2596 and a 80mm fan. Here goes nothing...
>>
>> On a different note, has anyone experimented with light pipes to bring
>> the PI's LED status to the front panel of a chassis? I've used the
>> Bivar SLP3-450-100-F on a NHRC Micro repeater controller previously
>> but the LEDs on the PI are too close together for those. I was looking
>> at the flexible Bivar LC-2.0 at the Mouser website and was wondering
>> if those might work. Any input from anyone?
>> --
>> Roger KJ4AJP
>>
>
>
>
>

Jim Thisdale

F.Y.I. Most computer mother boards have switch mode regulators on the board to make all the various voltages needed for the processor(s), memory, north & south

Message 53 of 53
, Apr 14, 2013

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F.Y.I.

Most computer mother boards have switch mode regulators on the board to make all the various
voltages needed for the processor(s), memory, north & south bridges, and various other hardware.
Gamer & enthusiasts boards often tout how many regulators/phases they have.

As for radiation, most of the noise is from the leads & tracks on the board of chips themselves,
especially when they are unshielded. A 5, 3.3, or even 1.8 volt signal toggling on-off at a high
rate can radiate quite a bit, with 32 or 64 bits wide all toggling at such high clock rates it will
radiate a lot of hash.... Computers tend to generate & radiate a lot of hash that's one reason the
better made ones have metal cases and metal shielding in key areas. The minor amount of noise/ripple
out of the supply is miniscule compared to the hash from the computer it-self. If a supply is truly
that noisy the noise/spikes on the power would be mistaken for data and foul up the processing.

On 4/7/13 6:15 AM, JJ wrote:
>
>
> On 13-04-07 05:49 AM, John B. Cundiff Jr. wrote:
>> Every time any digital device switches from off to on it produces a small spike and every spike
>> as harmonics or RFI ... you can never completely clean up the supply of a computer ...you must
>> design the computer
>> to live with the spikes and RFI.
>> On 04/07/13, Ray Wells<vk2tv@...> wrote:
>>
>> John,
>>
>> It's more than just spikes.
>>
>> The National Semiconductor recommendation to "tame" the output of the LM2596 smps is to add a
>> series inductor (10mH from memory) and a shunt capacitor. Whilst this may very well result in a
>> power supply that will "please" the Pi, it will do absolutely nothing to suppress RFI, which
>> requires techniques quite different from those that produce a clean DC supply. The problem is not
>> insurmountable but would require some devotion to produce a supply that is both DC and RF clean.
>> It can be done.
>>
>> FWIW, the problem, from a Pi perspective, isn't necessarily spikes. Some smps's produce a distinct
>> sawtooth output under load and whilst there may not be any spikes, there may well be dips below
>> the minimum working voltage of the Pi at the bottom of the sawtooth waveform.
>>
>> Don't believe for one moment that you can assess a supply as being "good" with a voltmeter,
>> digital or otherwise. It is indeed a case where a picture is worth a thousand words and that is
>> where the CRO plays its part. If you don't have a hardware CRO, use a soundcard based device.
>> There is plenty of free oscilloscope software available online.
>>
>> Ray vk2tv
>>
>>
>>
>> On 07/04/13 18:03, John B. Cundiff Jr. wrote:
>>> Wood not a simple choke ...maybe a torridal choke
>>> suppress the spikes every one is worried about .
>>> Put a big value filter capacitor afterwards .
>>> Be a lot more portable .. simpler and ..eleganter etc.
>>> On 04/06/13, Kerry McKenzie<kermck@...> wrote:
>>>
>>> Guys
>>> a rarely dumb question?
>>> how hard is it to just get an old pc power supply AT or ATX ,.... who
>>> cares either way,... you will get between 15 and 50 amps at 5 volts and
>>> throw a couple of caps across it.
>>> If you crow it,... it will be smooth
>>>
>>> if you go to any computer repair shop they will possible give you as
>>> many old ones as you want as most of them still work.
>>> i have 4 or 5 in my workshop down stairs and use them for all sorts of
>>> things and it so easy.
>>>
>>> my 2 cents worth.....Kerry
>>>
>>> PS Linux is still a bitch and I,m going nowhere with my projects ;-((
>>>
>>> --
>>> Kind Regards
>>> Kerry McKenzie
>>>
>>> PO Box 4492
>>> Kirwan QLD 4817
>>> Australia
>>>
>>
> yes, I agree...I use a vp-1020 satellite card in my computer and the P.S. noise is affecting the
> sensitivity of the card....my ham antennas are more than 100 feet from the house due to the rf
> racket produced by many switching power supplies in the house...even the darn router and cable modem
> supplies were awful, so running as much as I can directly from my solar system 12v rail...but there
> are just so many things nowadays that use these switching supplies it's hard to eliminate them
> all...oh, and then there's a neighbors samsung plasma tv .. 300 feet away from here and it wipes out
> my packet system when it's on...
> grr...
>
>
>
>

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